AntiretroviralUS FDA Database Verified

fosamprenavir (Rx)

Generic: Fosamprenavir

Brand: Lexiva, Telzin

(fos-am-pren'a-veer)

Pregnancy Category: C

Pharmacological Action

Prodrug of amprenavir; inhibits human immunodeficiency virus (HIV) protease, which prevents maturation of the infectious virus

Therapeutic outcome: Decreasing symptoms of HIV

Uses

HIV-1 infection in combination with antiretrovirals

Contraindications

Hypersensitivity to protease inhibitors

Precautions: Pregnancy C, breastfeeding, geriatric, liver disease, hemolytic anemia, diabetes, sulfa sensitivity, autoimmune disease with immune reconstitution

Dosage & Routes

Therapy-naïve patients

Adult: PO 1400 mg bid without ritonavir, or fosamprenavir 1400 mg/day and ritonavir 200 mg/day, or fosamprenavir 700 mg bid and ritonavir 100 mg bid Adolescent/child/infant $4 wk: PO 30 mg/kg bid, max 1400 mg/dose, without ritonavir Protease-experienced patients (PI)

Adult: PO 700 mg bid and ritonavir 100 mg bid Adolescent/child $20 kg: PO 18 mg/kg bid with ritonavir 3 mg/kg bid Adolescent/child 15 kg to ,20 kg: PO 23 mg/kg bid with ritonavir 3 mg/kg bid Adolescent/child 11 kg to ,15 kg: PO 30 mg/kg bid with ritonavir 3 mg/kg bid Adolescent/child ,11 kg: PO 45 mg bid with ritonavir 7 mg bid Infant $6 mo, 15 kg to ,20 kg: PO susp 23 mg/kg bid with ritonavir 3 mg/kg bid Infant $6 mo, 11 kg to ,15 kg: PO susp 30 mg/kg bid with ritonavir 3 mg/kg bid Infant $6 mo, ,11 kg: PO susp 45 mg/kg bid with ritonavir 7 mg/kg bid Combination with efavirenz

Adult: PO add another 100 mg/day of ritonavir for a total of 300 mg/day when all three products are given Hepatic dose

Adult: PO (Child-Pugh 5-6) 700 mg bid without ritonavir (treatment-naive patients) or 700 mg bid with ritonavir 100 mg qd (treatment-naive or experienced patients); (Child-Pugh 7-9) 700 mg bid without ritonavir (treatment-naive patients) or 450 mg bid with ritonavir 100 mg qd (treatment-naive or experienced patients); (Child-Pugh 10-15) 350 mg bid without ritonavir (treatment-naive patients) or 300 mg bid with ritonavir 100 mg qd (treatment-naive or experienced patients)

Available forms: Tabs 700 mg (equivalent to 600 mg amprenavir); oral suspension 50 mg/ml

Implementation -

Tabs: Administer without regard to food - Oral susp:

Adult: give without food; child: give with food; if vomiting occurs within 30 min, readminister; shake oral susp vigorously prior to dosing, use calibrated device - Patients receiving phosphodiesterase type 5 (PDE5) inhibitors may be at increased risk for PDE5 inhibitor adverse effects

Adverse Effects

CNS: Headache, fatigue, depression, oral paresthesia

GI: Nausea, diarrhea, vomiting, abdominal pain

INTEG: Rash, pruritus

MISC: Redistribution or accumulation of body fat, hyperglycemia, Stevens-Johnson syndrome

Pharmacokinetics

Absorption: Unknown

Distribution: 90% protein binding

Metabolism: In the liver by CYP3 A4

Excretion: Excretion of unchanged product is minimal

Half-life: Unknown

Pharmacodynamics

Onset: Unknown

Peak: 1½-4 hr

Duration: Unknown

Interactions

Individual drugs - Amiodarone, flecainide, lidocaine, midazolam, pimozide, propafenone, triazolam: serious life-threatening reactions CarBAMazepine, dexamethasone, efavirenz, lopinavir/ritonavir, nevirapine, phenytoin, ranitidine, saquinavir: decreased fosamprenavir levels, avoid concurrent use ARIPiprazole, itraconazole, ketoconazole, rifabutin, sildenafil, vardenafil: increased effect

Methadone: decreased effect

Warfarin: increased effect of warfarin Ritonavir with boceprevir or ritonavir with telaprevir not recommended: increased treatment failure Decreased dose of maraviroc with product is used with ritonavir; do not use maraviroc with unboosted fosamprenavir

Drug classifications

Antacids: decreased fosamprenavir levels - Barbiturates, proton-pump inhibitors, calcium channel blockers, ergots, H2 receptor antagonists: serious life-threatening reactions Contraceptives (oral): decreased effect Estrogens, H2 receptor antagonists, oral contraceptives, proton-pump inhibitors: avoid use; may lose virologic response and possibly lead to resistance of fosamprenavir HMG-CoA reductase inhibitors: increased toxicity

Drug/herb Avoid use with St. John's wort, may lose virologic response and possibly lead to resistance of fosamprenavir

Drug/lab test

Increased: serum glucose, AST, ALT, triglycerides

Nursing Considerations

Assessment - Assess bowel pattern before, during treatment; monitor hydration - Assess skin eruptions, rash, urticaria, itching -

HIV: Monitor viral load, CD4 cell counts, plasma HIV RNA, serum cholesterol, lipid profile baseline, throughout treatment - Stevens-Johnson syndrome: report immediately - Immune reconstitution syndrome: may occur with combination antiretroviral therapy; autoimmune disease may also develop, up to months after treatment starts

Patient/family education - Advise patient to avoid taking product with other medications unless directed by provider - Teach patient that product does not cure, but does manage symptoms; that product does not prevent transmission of HIV to others - Advise patient to use nonhormonal form of birth control while taking this product - Instruct patient if dose is missed, take as soon as remembered up to 1 hr before next dose; do not double dose - Instruct patient not to alter dose or stop therapy without talking to physician - Advise physician if patient has a sulfa allergy - Advise patient to report all medications, including herbal supplements, to prescriber

Evaluation

Positive therapeutic outcome: Decreasing symptoms of HIV

Reference

Mosby's Drug Guide; Davis Drug Guide

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